Background: Chronic recalcitrant dermatophyte infection (CRDI) remains poorly understood, with limited research on its genetic, immunological and treatment aspects.
Objectives: To investigate the genetic and immunological profiles, clinical characteristics and treatment outcomes in otherwise healthy patients with CRDI.
Methods: This was a prospective study of patients with isolated superficial dermatophyte infections persisting for > 5 years and refractory to at least three oral antifungal agents. Whole-exome sequencing, interleukin (IL)-17 quantification and lymphocyte subset analysis were performed.
Results: Of 5910 patients with superficial cutaneous fungal infections, 11 (10 men; 91%) with a mean (SD) disease duration of 26.4 (8.7) years were included in this study. All patients presented with extensive dermatophytosis, involving a mean (SD) of 5.6 (1.4) skin and nail sites. Immune alterations were identified in 55% (n = 6/11) of the patients, including three with monogenic immunodeficiency mutations (CARD9 and FOXN1), one with acquired immunodeficiency (Good syndrome) and two with isolated IL-17 deficiencies. Most patients (n = 10/11) showed a partial clinical response to continuous oral antifungal therapy, while only one patient remained a complete responder after discontinuing treatment.
Conclusions: CRDI is a rare condition in patients with superficial cutaneous fungal infections. Genetic and immunological evaluation for immunodeficiency should be considered in patients with CRDI. Management may require prolonged or lifelong oral antifungal therapy.
Fungal skin infections are common. They usually respond well to treatment. Some people have persistent infections that do not get better with standard medications. This condition is named ‘chronic recalcitrant dermatophyte infection’ (CRDI). In this study, we aimed to understand why these infections occur and how they can be better treated. We looked at whether problems with the immune system cause some patients to develop CRDI. We also assessed potential treatments. Of 5910 patients with fungal skin infections, 11 had CRDI. These patients had infections for over 5 years. They had not got better after trying at least three different medicines. We performed genetic and immune system tests to look for possible underlying causes. We found that CRDI is rare. It affects a tiny fraction of patients with fungal skin infections. More than half of our patients had problems with their immune systems. This suggests that immune system problems have a role in persistent infections. Most patients improved with continuous treatment. But, their infections came back when the treatment stopped. Patients with CRDI may have underlying problems with their immune system that make it harder for them to fight infections. Genetic and immunological testing can help identify such problems. Some patients may need long term or lifelong treatment to keep the skin infection under control. Understanding CRDI better can help doctors identify at-risk patients. It will also help improve treatment strategies for this challenging condition.
© The Author(s) 2025. Published by Oxford University Press on behalf of British Association of Dermatologists.